Multi-level parameter and frequency pulsing with a low angular spread

Abstract

Systems and methods for multi-level pulsing of a parameter and multi-level pulsing of a frequency of a radio frequency (RF) signal are described. The parameter is pulsed from a low level to a high level while the frequency is pulsed from a low level to a high level. The parameter and the frequency are simultaneously pulsed to increase a rate of processing a wafer, to increase mask selectivity, and to reduce angular spread of ions within a plasma chamber.

The invention claimed is: 
     
       1. A method comprising:
 controlling a radio frequency (RF) generator to generate an RF signal that concurrently pulses between a plurality of parameter levels and between a plurality of frequency levels during a time period, wherein the plurality of parameter levels include a first parameter level and a second parameter level, wherein the plurality of frequency levels include a first frequency level and a second frequency level, 
 wherein during the time period, a transition from the first frequency level to the second frequency level occurs in substantial synchronization with a transition from the first parameter level to the second parameter level and a transition from the second frequency level to the first frequency level occurs in substantial synchronization with a transition from the second parameter level to the first parameter level. 
 
     
     
       2. The method of  claim 1 , wherein said controlling the RF generator to generate the RF signal comprises:
 controlling the RF generator to transition the RF signal from the first parameter level to a third parameter level during a time period in which the RF signal has the second frequency level; and 
 controlling the RF generator to transition the RF signal from the third parameter level to the second parameter level. 
 
     
     
       3. The method of  claim 1 , wherein said controlling the RF generator to generate the RF signal comprises:
 controlling the RF generator to transition the RF signal from the first parameter level to a third parameter level during a time period in which the RF signal has the second frequency level; 
 controlling the RF generator to transition the RF signal from the third parameter level to a fourth parameter level during the time period in which the RF signal has the second frequency level; and 
 controlling the RF generator to transition the RF signal from the fourth parameter level to the second parameter level. 
 
     
     
       4. The method of  claim 1 , wherein said controlling the RF generator to generate the RF signal comprises:
 controlling the RF generator to transition the RF signal from the first parameter level to a third parameter level during a time period in which the RF signal has the second frequency level; 
 controlling the RF generator to transition the RF signal from the third parameter level to a fourth parameter level during the time period in which the RF signal has the second frequency level; 
 controlling the RF generator to transition the RF signal from the fourth parameter level to a fifth parameter level during the time period in which the RF signal has the second frequency level; and 
 controlling the RF generator to transition the RF signal from the fifth parameter level to the second parameter level. 
 
     
     
       5. The method of  claim 1 , wherein said controlling the RF generator to generate the RF signal comprises:
 providing a first digital pulse signal to the RF generator, wherein the plurality of parameter levels pulse in substantial synchronization with the first digital pulse signal; 
 providing a second digital pulse signal to the RF generator, wherein the plurality of frequency levels pulse in substantial synchronization with the second digital pulse signal, wherein the first digital pulse signal transitions among three or more logic levels and the second digital pulse signal is a clock signal that transitions between two logic levels. 
 
     
     
       6. The method of  claim 1 , wherein said controlling the RF generator to generate the RF signal comprises:
 controlling the RF generator to generate the RF signal that pulses in a stepwise increasing manner from the first parameter level via one or more additional parameter levels to the second parameter level in approximately the time period in which the RF signal pulses from the first frequency level to the second frequency level. 
 
     
     
       7. The method of  claim 1 , wherein said controlling the RF generator to generate the RF signal comprises controlling the RF generator to transition between the plurality of parameter levels in a stepwise manner. 
     
     
       8. The method of  claim 1 , wherein the second frequency level is greater than the first frequency level. 
     
     
       9. The method of  claim 1 , wherein the plurality of parameter levels include a plurality of voltage levels. 
     
     
       10. The method of  claim 1 , wherein the plurality of parameter levels include a plurality of power levels. 
     
     
       11. A controller comprising:
 a processor configured to:
 control a radio frequency (RF) generator to generate an RF signal that concurrently pulses between a plurality of parameter levels and between a plurality of frequency levels during a time period, wherein the plurality of parameter levels include a first parameter level and a second parameter level, wherein the plurality of frequency levels include a first frequency level and a second frequency level, 
 wherein during the time period, a transition from the first frequency level to the second frequency level occurs in substantial synchronization with a transition from the first parameter level to the second parameter level and a transition from the second frequency level to the first frequency level occurs in substantial synchronization with a transition from the second parameter level to the first parameter level; and 
 
 a memory device coupled to the processor. 
 
     
     
       12. The controller of  claim 11 , wherein to control the RF generator to generate the RF signal, the processor is configured to:
 control the RF generator to transition the RF signal from the first parameter level to a third parameter level during a time period in which the RF signal has the second frequency level; and 
 control the RF generator to transition the RF signal from the third parameter level to the second parameter level. 
 
     
     
       13. The controller of  claim 11 , wherein to control the RF generator to generate the RF signal, the processor is configured to:
 control the RF generator to transition the RF signal from the first parameter level to a third parameter level during a time period in which the RF signal has the second frequency level; 
 control the RF generator to transition the RF signal from the third parameter level to a fourth parameter level during the time period in which the RF signal has the second frequency level; and 
 control the RF generator to transition the RF signal from the fourth parameter level to the second parameter level. 
 
     
     
       14. The controller of  claim 11 , wherein to control the RF generator to generate the RF signal, the processor is configured to:
 control the RF generator to transition the RF signal from the first parameter level to a third parameter level during a time period in which the RF signal has the second frequency level; 
 control the RF generator to transition the RF signal from the third parameter level to a fourth parameter level during the time period in which the RF signal has the second frequency level; 
 control the RF generator to transition the RF signal from the fourth parameter level to a fifth parameter level during the time period in which the RF signal has the second frequency level; and 
 control the RF generator to transition the RF signal from the fifth parameter level to the second parameter level. 
 
     
     
       15. The controller of  claim 11 , wherein to control the RF generator to generate the RF signal, the processor is configured to:
 provide a first digital pulse signal to the RF generator, wherein the plurality of parameter levels pulse in substantial synchronization with the first digital pulse signal; 
 provide a second digital pulse signal to the RF generator, wherein the plurality of frequency levels pulse in substantial synchronization with the second digital pulse signal, wherein the first digital pulse signal transitions among three or more logic levels and the second digital pulse signal is a clock signal that transitions between two logic levels. 
 
     
     
       16. The controller of  claim 11 , wherein to control the RF generator to generate the RF signal, the processor is configured to:
 control the RF generator to generate the RF signal that pulses in a stepwise increasing manner from the first parameter level via one or more additional parameter levels to the second parameter level in approximately the time period in which the RF signal pulses from the first frequency level to the second frequency level. 
 
     
     
       17. The controller of  claim 11 , wherein to control the RF generator to generate the RF signal, the processor is configured to control the RF generator to transition between the plurality of parameter levels in a stepwise manner. 
     
     
       18. The controller of  claim 11 , wherein the second frequency level is greater than the first frequency level. 
     
     
       19. The controller of  claim 11 , wherein the plurality of parameter levels include a plurality of voltage levels. 
     
     
       20. The controller of  claim 11 , wherein the plurality of parameter levels include a plurality of power levels. 
     
     
       21. A system comprising:
 a radio frequency (RF) generator; and 
 a controller coupled to the RF generator, wherein the controller is configured to:
 control the RF generator to generate an RF signal that concurrently pulses between a plurality of parameter levels and between a plurality of frequency levels during a time period, wherein the plurality of parameter levels include a first parameter level and a second parameter level, wherein the plurality of frequency levels include a first frequency level and a second frequency level, 
 wherein during the time period, a transition from the first frequency level to the second frequency level occurs in substantial synchronization with a transition from the first parameter level to the second parameter level and a transition from the second frequency level to the first frequency level occurs in substantial synchronization with a transition from the second parameter level to the first parameter level. 
 
 
     
     
       22. The system of  claim 21 , wherein to control the RF generator to generate the RF signal, the controller is configured to:
 control the RF generator to transition the RF signal from the first parameter level to a third parameter level during a time period in which the RF signal has the second frequency level; and 
 control the RF generator to transition the RF signal from the third parameter level to the second parameter level. 
 
     
     
       23. The system of  claim 21 , wherein to control the RF generator to generate the RF signal, the controller is configured to:
 control the RF generator to transition the RF signal from the first parameter level to a third parameter level during a time period in which the RF signal has the second frequency level; 
 control the RF generator to transition the RF signal from the third parameter level to a fourth parameter level during the time period in which the RF signal has the second frequency level; and 
 control the RF generator to transition the RF signal from the fourth parameter level to the second parameter level. 
 
     
     
       24. The system of  claim 21 , wherein to control the RF generator to generate the RF signal, the controller is configured to:
 control the RF generator to transition the RF signal from the first parameter level to a third parameter level during a time period in which the RF signal has the second frequency level; 
 control the RF generator to transition the RF signal from the third parameter level to a fourth parameter level during the time period in which the RF signal has the second frequency level; 
 control the RF generator to transition the RF signal from the fourth parameter level to a fifth parameter level during the time period in which the RF signal has the second frequency level; and 
 control the RF generator to transition the RF signal from the fifth parameter level to the second parameter level. 
 
     
     
       25. The system of  claim 21 , wherein to control the RF generator to generate the RF signal, the controller is configured to:
 provide a first digital pulse signal to the RF generator, wherein the plurality of parameter levels pulse in substantial synchronization with the first digital pulse signal; 
 provide a second digital pulse signal to the RF generator, wherein the plurality of frequency levels pulse in substantial synchronization with the second digital pulse signal, wherein the first digital pulse signal transitions among three or more logic levels and the second digital pulse signal is a clock signal that transitions between two logic levels. 
 
     
     
       26. The system of  claim 21 , wherein to control the RF generator to generate the RF signal, the controller is configured to:
 control the RF generator to generate the RF signal that pulses in a stepwise increasing manner from the first parameter level via one or more additional parameter levels to the second parameter level in approximately the time period in which the RF signal pulses from the first frequency level to the second frequency level. 
 
     
     
       27. The system of  claim 21 , wherein to control the RF generator to generate the RF signal, the controller is configured to control the RF generator to transition between the plurality of parameter levels in a stepwise manner. 
     
     
       28. The system of  claim 21 , wherein the second frequency level is greater than the first frequency level. 
     
     
       29. The system of  claim 21 , wherein the plurality of parameter levels include a plurality of voltage levels. 
     
     
       30. The system of  claim 21 , wherein the plurality of parameter levels include a plurality of power levels.